Consciousness. A simple word, but what does it mean? As you sit here reading this paper you may be conscious of many things: the itch on the back of your leg, the rain falling outside your window, as well as what you are reading right now. You can be conscious of many things, yet you are not conscious of everything you could be. Are you aware of each letter that you are reading right now, the exact time, or how many days until Christmas? You know the answer to every one of these questions, but you were not conscious of the answers until you read the questions. You are conscious of certain things at certain times. This roundabout explanation of consciousness is necessary because there is no clear definition of the term. The Oxford English Dictionary [38] defines consciousness as ``the totality of the impressions, thoughts, and feelings that make up a person's conscious being,'' and being conscious as being ``aware of what one is doing or intending to do, having a purpose and intention of one's actions.'' Since you are able to access your thoughts, you know that you are an individual with consciousness. Yet, how do you know if I am an individual with consciousness? One further question remains: do the rest of the animals possess consciousness?

Studies have repeatedly tried to prove consciousness in animals through observations of their behaviors and brains. This paper examines five areas that can be considered indirect evidence of consciousness: self-awareness, problem solving, use of language, deceit, and neurological similarities to the human brain. These studies are not accepted by all as clear evidence; many individuals proclaim that the circle of organisms who possess conscious thoughts and actions contains only humans [10]. Based on recent evidence, how small is the circle of consciousness?

Humanity has been questioning the existence of animal consciousness for many years. The first known theory on this subject was animism, the idea that every moving thing has a mind or soul [12]. As our species grew the prevailing idea remained that our thoughts were not special or different. Aristotle believed that everything acts to reach a goal - ``to `fulfill' itself'' [22]. The first to disagree with this long-held belief was Francis Bacon in the 1600s, with the hypothesis that our beliefs were due to our tendency to see ourselves in everything. Benedict de Spinoza agreed, adding that the observer would see an animal attempting to reach a goal only because the observer is always trying to reach a goal [22].

Darwin's theory of evolution was a turning point for the biological sciences because it provided evidence for a physiological continuity between us and the other animals. He hypothesized that this discovery could also show that there was a continuity in our minds [2]. After conducting research on his predictions with George John Romanes, these two concluded that the continuity of the mind extended to all animals, especially dogs and primates [32]. He stated that ``there is no fundamental difference between man and the higher mammals in their mental facilities'' [26]. Darwin's studies can be considered the first step towards a scientific study of the animal mind.

One aspect of consciousness is self-awareness. To test self-awareness, an animal's reaction when confronted with a mirror image is observed. Experiments have shown that both higher primates (gorilla, chimpanzees, and orangutans) and dolphins are able to learn that the image in the mirror is their own image [34]. They often use the mirror to examine things they would not be able to see without it: their genitalia, a spot of paint added to their heads by a scientist, and parts of their faces [34]. For many, the actions involved prove that the animals are conducting ``self-directed behavior.'' The conclusion is that they act in this way because they are aware that the image that they are seeing is their own.

A different test of self-awareness is examining if an animal can recognize input from another knowledgeable source. Repeated tests were given to chimpanzees to see if they could make a correct decision as to where a treat was placed by inferring from the knowledge of human observers (thus demonstrating an understanding of another's mind). A researcher that the chimpanzee observed watching the hiding of the food (the knowledgeable source) would point to a cup that hid the food, while another researcher, that the chimpanzee knew was not present earlier, pointed to an incorrect cup. The results showed that the chimps chose the correct container for a statistically significant amount of trials just by ``listening'' to the knowledgeable human, and ignoring the one that could not know the location of the food [34].

Some of the earliest experiments that attempted to prove animal consciousness used problem-solving as a basis. The theory behind using this approach is that if an animal can create a plan to act on, it is thinking consciously about the problem. During the First World War, Wolfgang Köhler, a psychologist, studied the chimpanzee's ability to reason. He hung a bunch of bananas out of reach from the animal, and left objects in the cage that could be used to reach the food. Although a few of the chimpanzees did get the food by stacking crates to reach it, or joining sticks to knock it down, it took them many trials to do so [12]. Due to the large numbers of trials necessary for the animals to reach the food, this result can be seen as an artifact of chance, not evidence of reasoning ability [34]. These animals did not necessarily visualize the solution and work out a plan, they just kept trying. As Marian Stamp Dawkins [10] explains, just because an animal can perform a complex behavior does not mean that it has conscious thought.

Recent studies look for more conclusive evidence for the ability to reason in animals. A few excellent examples come from studies conducted by D. J. Gillan using chimpanzees as subjects. Series of tests were given to a 16-year-old chimpanzee named Sarah, who had previously had language training. This is important information to take note of because an animal taught language may then use a different way to organize their thoughts, and have a different perspective on reasoning problems. Sarah's ability to judge the equivalence of two distinct objects, and then use her observations to decide how to complete a different pair of objects, was tested. The first experiment used geometric figures. The initial pair of objects (A and A') would be identical except for one difference. Sarah was then given a new geometric structure (B), and a choice of two objects to pair it up with. One of the choices (B') had the same difference from the new geometric structure (B) as the difference between the two original objects. Sarah chose correctly 85% of the time [15].

Sarah's reasoning abilities were examined further with additional analogies. One test had her decide whether already paired objects formed an analogy. She was correct 72% of the time for these [15]. The most informative test was a conceptual analogy test, because it is most like human analogical reasoning. If an animal could solve a problem similar to one that a human needs to consciously analyze, we may be able to infer that the animal also consciously made the decision. As in the first test, Sarah had to complete analogies, but now she needed to recall characteristics of the objects from her long-term memory. One analogy problem involved determining the relationship between paper and scissors and extending this relationship to an apple and either a knife or a plate. The correct answer for the question is ``knife.'' To make sure Sarah was not just answering ``knife'' because it has a stronger association with apple she was always given a second problem with the same stimulus (apple) and the same alternatives (knife, plate), but a different analogy. An example of this could be ``lid is to jar as apple is to either knife or plate'' [15, p. 183]. This example shows that Sarah had to visualize her experience with these objects and then convey to the tester how she remembered them. This was not a simple memory test because she was given unique and novel situations, and answered by evaluating her own knowledge.

The previous example problems are all in some way similar to reasoning problems given to humans. To see what reasoning a chimpanzee may use normally the tests needed to be adjusted. Four chimpanzees who were not previously trained in language were trained to choose between two food sources. For one source, they were given the knowledge that the food may no longer be there (negative information about the food source). The first experiment had the subject observe another chimpanzee take the food from one of the sources and walk away. The observer (correctly) chose the other food source, on average, 94% of the time. The second experiment had the subject observe a chimpanzee on a path walking away from one of the food sources, but did not see the animal take the food. For this experiment the observer was only correct 54% of the time. The third experiment had a chimpanzee observe another chimpanzee going towards one of the food sources, and then later observe the same chimpanzee with food. The subject was correct 88% of the time [15]. The conclusions that can be drawn from these experiments are that chimpanzees can reason, and they do so more accurately when given more clues.

A final experiment was conducted with only two chimpanzees (Sadie and Luvie), with interesting results. The subject saw both food source locations baited with a certain type of fruit, one with an orange and one with an apple. Each subject was later presented with a chimpanzee holding one of the fruits, and was then allowed to choose to go to one of the food sites. One chimpanzee chose the location with the other type of fruit a significant amount of times (10 out of 12). A conclusion from this result is that the animal reasoned that a chimpanzee with the food from a certain location meant that the food was no longer at that location. Yet, the other chimpanzee repeatedly chose the spot that had the same food as what the other chimpanzee was holding (75% of the time). How could one chimp answer correctly so often, while the other normally answered incorrectly? The conclusion Gillan drew was that the second chimpanzee was choosing the location of the piece of fruit that the other chimps had because the fruit reminded her of that location. Therefore, both of these animals reasoned, but in different ways [15].

From these experiments it seems clear that at least some animals do reason. The animals seem to analyze these complex problems in their minds, ``consciously'' examining different answers to the problems presented to them. Even though this evidence is very strong, it does not completely show that animals possess the reasoning abilities of man. In different analogy experiments Sarah was given choices of answers that varied in their order. The chimpanzee got very few of these answers correct.

Studies have shown that many animals do have amazing problem solving and reasoning abilities (even if they are different from human reasoning). These animals are able to manipulate their environment in seemingly conscious ways, but are they truly aware of themselves and their actions?

One of the most studied and widely debated pieces of evidence for animal consciousness is the use of communication. There are two major parts to the argument that communication cannot be a proof of consciousness. The first is that true language is needed for consciousness. The idea behind this is that to have complete abstract thoughts one needs language to organize and communicate them. The second part to this argument is that animal communication is not sophisticated enough to be language. Donald Griffen, the first to define the study of animal mental states as cognitive ethology, feels that the view that there is no thought without language is incorrect. In addition, he feels that some animal communications are so close to language that the entire argument may be without a basis [21].

In recent years American sign language (ASL) has been taught to chimpanzees, bonobos, and gorillas. This language is used because it was found that these species do not have vocal cords that enable them to communicate with a spoken human language. The first to be taught ASL was Washoe, a female chimpanzee. After four years of training she was able to sign 132 words, and string them together into short coherent phrases. Most of the words and phrases were taught to Washoe by humans, yet a significant number of signs were of her own creation [34], [21]. Apes are not only able to be taught new modes of communication through human instructors. Some have been taught by placing them as infants in the care of an adult ape that could use the language, or allowing them to observe another ape being trained. A bonobo named Kanzi learned by observation. Kanzi's adopted mother, Matata, was being taught a language of lexigrams, geometric shapes that represent words. When Kanzi was 30 months old he was separated from Matata, and spontaneously began to use the lexigrams to communicate. Approximately half of Kanzi's productions were spontaneous, with most of these being communications of requests [44]. Besides learning how to understand and speak ASL, many of the apes that have been taught sign language are able to understand spoken English [21].

It has been shown that higher primates can be taught some aspects of language, but are they able to communicate on their own without human instruction? There are many instances where researchers have observed chimpanzees using their own sign ``language'' to communicate. Jane Goodall has clearly found that wild chimpanzees use different gestures of the face, hands, and the rest of the body to communicate effectively with one another [17] . Other researchers have found that captive chimpanzees also have a gesture based communication system [21]. These findings are impressive, but not without problems. In most texts it is stated that human investigators have yet to decipher the gestures, so this evidence is easily refuted by saying that the scientists are seeing something that just is not there. Jane Goodall disagrees. When asked if she had any idea what these gestures and postures could mean, she was amused. She feels that these gestures are so similar to the gestures humans make that they mean the same things [17]. But this could again be seen as someone reading too much into the actions of an animal. Are these amazing methods of communication seen in animals evidence of language? It seems that these animals are able to communicate from sender to receiver, as well as represent their environment by external and perhaps internal representations. One approach to finding differences between animal communication and human language has been to decide what the basic traits of human language are and then compare these factors to data from animal studies. In one analysis, done by Hockett, it was decided that displacement, productivity, and duality of patterning were characteristics of only human language.

Displacement is the ability of the sender of the communication to refer to things that are displaced in time and space, or things that can never occur. It cannot simply be a delay in time, or a movement in space. The honey bee waggle dances are distanced in time and space from the object of the communication, the food source, but not removed from the object [44]. Compare this to a discussion that could occur between the two of us. We could discuss the decline of Rome, which is remote to us in both time and space. The question of whether the characteristic of true displacement has been clearly shown in the animal world has created disagreement. The animals seldom use language spontaneously and the signs apes use are predominantly requests [30]. The subject of the communication is therefore not remote. What about the ``utterances'' that are not requests or mimicry - do these demonstrate productivity? At one time Washoe saw a swan, and signed ``water bird.'' She had never been taught this unique sign, so did she create her own? Perhaps she just happened to sign ``bird,'' and then ``water'' because those were things in her visual field [30]. It is obvious that the interpretation attributed to the utterance is important.

A different area in the question of animal language addresses whether animals possess a grammar in their own communications, or if they can use grammatically correct sentences when taught a human language. Many have come to the conclusion that there is little evidence for any type of grammar. Project Nim was started in 1973 by H. S. Terrace [41] with the purpose of finding if a chimpanzee ``could use one or more rules of finite-state grammar.'' Nim, and most other apes only form small word groupings. Yet, even though most of Nim's signs consisted of two-sign combinations, they might have been primitive sentences because in many situations Nim used certain signs in a certain position, no matter what the word was paired with. Although some of Nim's short phrases may have some sort of syntax, his longer phrases seem nothing more than repetitions for emphasis. His longest utterance, 16 signs, seems just to emphasize his desire for a piece of fruit: ``give orange me give eat orange me eat orange give me eat orange give me you'' [41].

In an experiment conducted by E.W. Menzel, Jr., a single chimpanzee was separated from its group, and shown an area where food was hidden in an enclosure, and then returned to the others. When the entire group was released into the enclosure, the animal sometimes behaved as if he did not want to share the food, by attempting to conceal its location [21]. R. Byrne and A. Whiten observed an interesting example of a behavior that could be classified as deceit in baboons. An adolescent that often acted as a bully was observed bothering a younger baboon. When the younger baboon screamed, all the adults came running, while the adolescent immediately took on a posture indicating a predator's approach. None of the human observers were able to see any predator, and concluded that the adolescent expected a punishment from the adults and to distract them created a false alarm. This animal may have been consciously creating a situation to get itself out of trouble [34].

Many scientists have tried to examine the human brain to find what may cause consciousness in us, and then compare these structures to animal brains. If close similarities exist between the parts of our brains responsible for higher thought functions, and structures in animal brains, these similarities could be evidence for a continuity of thought, and therefore a possible continuity of consciousness.

The first characteristic many studied was size of brain mass compared to intelligence. H.J. Jerison's ``Principal of Proper Mass'' explains this idea by stating that the ``mass of a given neuronal population that performs a particular function will be in proportion to the extent to which that function is performed'' [23, p. 94]. An example of this is the large visual systems of birds and primates, correlated with the importance of vision in these animals [23]. With few exceptions, an increasing encephalization quotient, relative size of the brain to body size, has been shown to correlate with increasing intelligence between species. In addition, as the proportions of glia cells to neurons increase there is an increase in perceived intelligence, as well as brain size. So, this evidence does show a continuity [5].

Many who have looked at more specific characteristics have also found evidence of similarities between specific structures in animal and human minds. Lateralization of the brain is the specialization of different parts of the left and right half of the brain for certain tasks. This organization is not only seen in human brains, it has also been observed in non-human animals through observation of ``handedness'' [5]. Additional studies have looked at the similarities of the chemical and electrical processes of animal and human brains. Studies have found that humans react in similar ways to psychotherapeutic drugs as animals. If a human acts in an unusual way because of a change in conscious thought due to a drug, and an animal given the drug acts in the same way possibly the two are both thinking consciously. Additional evidence shows that animals have similar EEGs while sleeping to those humans have while dreaming. Event-related potentials (ERPs) have also been measured for a number of animals and found to be similar to humans in different ways. This may be pertinent to the discussion of consciousness because late cortical waves (after 100 msec) have been associated with decision making, and expectation of certain events. There have been especially distinct similarities shown between the occurrences of these waves in humans and other primates [5].

There is still much to learn in the area of neuroscience about our own brains, so the future may hold discoveries that could further encourage the idea of animal consciousness, or dismiss it. New advances could radically change our perceptions of the animal world. Very recently it was discovered that the size of the planum temporale in chimpanzees is asymmetrical, similar to the asymmetry of human language areas [17].

There is too much evidence to rule out the possibility that animals have consciousness, but there is not enough to conclude that they do. Possibly there are differences between our thoughts and animals' thoughts, but humans cannot be hugely different from animals, because we are animals. We evolved from the same processes, and are descended from the same organisms.

Yes, we are spectacular creatures who have amazing abilities, but so are other animals, and perhaps our abilities are not so different. Can a young child give directions to a food source more accurately than a bee, can a moderately retarded person draw better conclusions than a chimpanzee from just one clue? Do these possibilities mean that children and human individuals of lower intelligence are without consciousness? I doubt that many could support that conclusion. Yes, humans have different levels of intelligence that force individuals to see the world differently. Perhaps consciousness should be looked at as a matter of degrees. Perhaps a human has more awareness than a chimpanzee, and the chimpanzee more awareness than a bird. A human may need to be aware of the remotely occurring process of the death of a star, while a bird may need to be aware that calling its friends to the sight of food may save its life. One can ignore the research and hold tight to the idea of a circle of consciousness that only includes humans, but I no longer believe that the answer is that simple and that the circle is that small.